A conveyer apparatus, such as an escalator and a moving walkway, includes a plurality of footsteps provided with footstep rollers. Since these plural footsteps are linked to each other at predetermined pitches through an endless footstep chain driven by a chain drive mechanism, the footsteps are integrated with the footstep chain and are all constructed so as to move synchronously while leaving no space therebetween. Additionally, due to is an engagement of the footstep rollers with a footstep guide rail disposed in a structure, these plural footsteps are adapted so as to move between an entrance and an exit circulatively while being supported by the footstep guide rail. Noted, for the reason that a plurality of footsteps of a moving walkway generally move in a horizontal direction, the footsteps may be called footplates in some cases. In this specification, however, the notation will be unified to footsteps also in case of the moving walkway.
As the chain drive mechanism to drive the footstep chain, it is general that a turn-over end of the footstep chain is wound around a drive sprocket rotating on receipt of a driving force of a drive motor, while the driving force of the motor is transmitted to the footstep chain through the drive sprocket. Such a chain drive mechanism is normally accommodated in a structure called a truss near an entrance of the conveyer apparatus or an exit thereof.
Meanwhile, it has been heretofore thought that the truss accommodating the chain drive mechanism requires enough space for its installation work. In recent years, however, the miniaturization of truss is accomplished by the progress of installation technique etc. As a result, there are carried out attempts to make the whole conveyer apparatus thin in order to save its installation space. If the truss is miniaturized in the above-noted manner, then it is required to use a small-diameter sprocket for the drive sprocket of the chain drive mechanism. However, the utilization of such a small-diameter sprocket for the drive sprocket of the chain drive mechanism may cause the footstep rollers linked by the footstep chain to move at a moving velocity with a relatively great unevenness. This velocity unevenness of the footstep rollers causes vibrations of the footsteps, so that the riding quality of the conveyer apparatus is deteriorated.
For example, Japanese Patent Application Laid-open (Hei) No. 8-217368 proposes a technique to suppress such a velocity unevenness for smooth movement of the footstep rollers. According to the technique disclosed in Japanese Patent Application Laid-open (Hei) No. 8-217368, as is shown in FIG. 1, a relative positional relationship between a footstep guide rail 102 and a drive sprocket 103 is established so that a bearing surface (traveling track) 102a of the footstep guide rail 102 linked by a footstep chain 100 is positioned apart from a tangential line 103a of the drive sprocket 103 by an interval ho. Further, a compensating rail 104 is arranged on the leading side of the footstep guide rail 102 adjacent to the drive sprocket 103. In this compensating rail 104, its bearing surface (traveling track) 104a for supporting footstep rollers 101 has the same height, on its side close to the footstep guide rail 102, as that of the bearing surface 102 of the footstep guide rail 102 and has also the same height, on the side close to the drive sprocket 103, as that of a groove in mesh with the footstep roller 101 of the drove sprocket 103. Further, an intermediate portion of the bearing surface 104a is curved smoothly. In operation, the footstep rollers 101 traveling while being supported by the bearing surface 104a of the compensating rail 104 are engaged with the groove of the drive sprocket 103 via the rollers' linear motion and the next curvilinear motion and thereafter, the rollers 101 rotate corresponding to the rotation of the drive sprocket 103. The velocity unevenness of the footstep rollers 101 is suppressed by the above-mentioned movements of the rollers.
Although the above-mentioned prior art enables the velocity unevenness of the footstep rollers 101 to be suppressed effectively, it is disadvantageous in view of the thin formation of the conveyer apparatus as a whole since the footstep guide rail 102 is positioned higher than the drive sprocket 103. In detail, as the interval ho between the tangential line 103a of the drive sprocket 103 and the bearing surface 102a of the footstep guide rail 102 has a value proportional to a link length of the footstep chains 100, the link length of the footstep chain 100 in relation to the drive sprocket 103 becomes a relatively great value especially in case of using a small-diameter sprocket for the drive sprocket 103. As a result, the interval ho between the tangential line 103a of the drive sprocket 103 and the bearing surface 102a of the footstep guide rail 102 grows larger. Thus, the truss is large-sized to be an obstacle to the thin formation of the conveyer apparatus as a whole.
Further, considering a situation where outward and homeward routes are reversed to operate the conveyer apparatus, it is necessary to establish also the homeward side of the footstep guide rail 102 under the drive sprocket 103 at the similar interval ho, thereby requiring a considerable height of the apparatus for such upper and lower intervals (2×ho).
Provided that the drive sprocket 103 is formed with 348.4 mm in the diameter of pitch circle and eight teeth and the link length of the footstep chain 100 is 133.33 mm, the interval ho between the tangential line 103a of the drive sprocket 103 and the bearing surface 102a of the footstep guide rail 102 has to be more than 35.3 mm in order to completely eliminate the velocity unevenness of the footstep roller 101 in the above-mentioned prior art, according to the inventors' trial calculation. Further totalizing both the outward side and the homeward side of the apparatus, it is necessary for the apparatus to make sure of an extra height of 70.6 mm (2×ho) in addition to the size of the drive sprocket 103. Thus, it results in spoiling the space-saving effect that is brought by reducing the diameter of pitch circle of the drive sprocket 103 down as far as 348.4 mm.